1. Field of the Invention
The present invention generally relates to an air damper, and more specifically, to an improved structure of a cylindrical air damper installed in, for example, the glove box of an automobile, which can efficiently prevents dust from entering the cylinder.
2. Description of the Related Art
A cylindrical air damper of the earlier technology is disclosed in, for example, Japanese Patent Application Laid-open No. 2000-65116. This type of air damper includes a cylinder having openings at both ends, and a piston movable in the cylinder while keeping tight contact with the inner face of the cylinder. A piston rod that has a cross-shaped cross sectional view is coupled to the piston. The piston rod extends through the opening of one end of the cylinder. A cap is provided to the other end of the cylinder so as to be slightly movable in response to a pressure change in the cylinder. A fin-like fixing piece extends from the outer surface of the cylinder near the other end. An annular shelf (or platform) is formed in the inner surface of the cylinder near the other end. This annular shelf becomes a sealing face that comes into contact with the cap.
When using the conventional air damper in the glove box of an automobile, the other end of the cylinder is fixed to the instrument panel of the automobile via the fixing piece in a pivotable manner. The piston rod is fixed to the glove box. When the glove box is opened, the piston rod is pulled out of the cylinder via the opening, while causing the piston move along the cylinder. The pressure change in the cylinder causes the cap to come into tight contact with the sealing platform. In this state, the air flow is only allowed via the orifices formed in the base of the cap, which produces a damper effect and allows the glove box to open gently.
When closing the glove box, the piston rod is inserted slowly into the cylinder, and the piston moves in the same direction. The motion of the piston causes a pressure change in the cylinder, and due to the pressure change, the cap separates from the sealing platform (or the sealing face). Consequently, the air flows out of the cylinder, and the piston can move smoothly in the cylinder. This allows the glove box to be closed promptly.
Although the conventional air damper realizes a simple one-way air damper that makes use of a pressure change to cause the cap to engage with and disengage from the sealing platform, dust is easily accumulated in the space defined by the cross-shaped piston rod. The dust accumulated in the piston rod is likely to enter the cylinder during the operation of the piston. Once the dust enters the cylinder, the friction between the piston and the cylinder increases, and the interface between the cylinder and the piston is damaged or worn out.
The present invention is conceived to overcome these problems in the air damper of the earlier technology.
In one embodiment, the air damper comprises a cylinder having a first opening and a second opening, a piston that moves in the cylinder, a piston rod coupled to the piston and moving in and out at the first opening of the cylinder, and a cap positioned at the second opening of the cylinder. The piston rod has a continuous outer wall and an opening extending along the longitudinal axis of the rod. The cap has an orifice and a sealing flange.
The piston rod has an inverse U-shaped cross-section taken along a plane perpendicular to the longitudinal axis of the rod. Alternatively, the cross-sectional view of the piston rod may be an inverse V-shape, C-shape, or the like. The piston rod may take any shape as long as it has a continuous outer wall and an opening.
The piston rod has a fixing ring at a leading end. A plane containing the opening of the piston rod is perpendicular to a plane defined by the fixing ring. Alternatively, the plane containing the opening of the piston rod can be parallel to the plane defined by the fixing ring.
In another aspect of the invention, an air damper used to control a motion of a movable body relative to a fixed body is provided. This air damper comprises a cylinder having a first opening and a second opening, a piston that moves in the cylinder, a piston rod coupled to the piston and having a continuous outer wall and an opening extending along the longitudinal axis of the rod, the piston rod being fixed to either the movable body or the fixed body with the opening facing downward. A cap having an orifice and a sealing flange is positioned at the second opening of the cylinder.
In still another aspect of the invention, an air damper used to control a motion of a movable body relative to a fixed body comprises a cylinder having a first opening and a second opening, a piston that moves in the cylinder, a piston rod coupled to the piston and having a continuous outer wall and an opening extending along the longitudinal axis of the rod, piston rod being fixed to the movable body so that the opening faces the movable body.
In still another aspect of the invention, an air damper used to control a motion of a movable body relative to a fixed body comprises a cylinder having a first opening and a second opening, a piston that moves in the cylinder, a piston rod coupled to the piston and having a continuous outer wall and an opening extending along the longitudinal axis of the rod, the piston rod being fixed to the fixed body so that the opening faces the fixed body.